The survey, published on Thursday, spoke to more than 2,500 school and university students in the UK and found 60% of respondents watch porn to get information about sex – despite almost 75% saying that it creates unrealistic expectations.

Of the students surveyed, 75% say the sex education at their school was not practical and rated it as either fair, poor, or terrible. On top of this, 50% say issues they need to know about are not covered in class.

Jane Lees, chair of the Sex Education Forum, says: “Consent and relationship safety are real issues affecting students and sadly they are leaving school with little or no discussion on these topics having taken place.”

Friends, school, and sexual partners were listed as the top three sources relied upon for information. However according to those surveyed, the topics covered in class were more biology based – with puberty, contraception, sexual health, and bodies and anatomy listed as the most commonly taught.

In contrast, consent was never touched upon for 75% of respondents, and relationships were covered for less than 50%. Under a fifth discussed LGBT issues and 75% felt the education they received was not diverse enough.

Jack Wallington, director of community at the Student Room, says: “These findings mirror the comments we hear from young people everyday – that the UK’s sex and relationships programmes are patchy, at best.

“Students regularly report a general lack of practical advice and inadequate or incorrect information about sexuality, contraception and STIs – leaving a black hole of unanswered questions that are filled by friends and websites.

“We’d like to see greater standardisation in sex and relationships education programmes, and ones which directly address the needs of young people, instead of leaving them to hunt for pieces of the puzzle themselves.”

The NUS and Sex Education Forum are calling for sex and relationship education to be statutory in schools. Of the survey respondents, 90% agree that it should be made compulsory.

Colum McGuire, vice president of NUS, says: “Sex and relationship education is failing millions. People are being left with gaps in their education and [this] puts young people at risk. I find it alarming that sexual partners are listed as a top SRE source. Consider this in light of the fact that consent was never raised for two thirds of respondents [and that] the current system almost completely ignores LGBT relationships.

“We urge all political parties to commit to statutory SRE in their general election manifestos, and to accept that simple biology just won’t cut it.”

Statutory status would allow SRE to be treated in the same way as other compulsory subjects, with teachers receiving training and time allocated in school timetables for teachers to address real-life issues with students, including respectful relationships, consent and LGBT issues.